ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
415 
or no value in other cases, and though liable to vary with external con- 
ditions, yet it is worthy of study. The method suggested is the insertion 
of a diaphragm in the ocular of the microscope, a rectangular opening 
.{2 mm. square) having been cut in the diaphragm. The actual dimen- 
sions of the square field thus obtained are then measured with a stage 
micrometer. Then, if in this field of n sq. mm. one can count c cells in 
a given mpss leaf, the total number of cells in a sq. mm. is the “ cellular 
index,” c : n. The best method of employment and some necessary 
precautions are described. Examples are given, and a striking table of 
the results arising from the application of the method to the species of 
Mnium. A. G. 
Cellular Index of European Fissidens of the Crassipes Group. — 
J. Amann {Revue Bryologique , 1921, 65-9). The author applies his 
cellular index method to six species of Fissidens of the Crassipes group, 
and gives the measurements of numerous examples, together with the 
conclusions which he draws. A. G. 
Observations on Some Species of the Genus Fissidens. — R. 
Potier DE LA Varde {Revue Bryologique , 1914, 85-92, 94-8 ; 1920, 
17, 18, 33-5 ; 1921, 5-9, 70-2 ; 1922, 1-5, 4 figs.). Critical notes 
arranged under the following headings : (1) Preliminary remarks on 
the specific value of apparent dicecism. (2) Fissidens tamarindifolius : 
is it really a specific type ? (3) Remarks on F. gracilis (La Pyl.) Brid. 
(4) Concerning F. Lylei Wils. (5) On the presence of F. Monguilloni 
Ther. in Mayenne and in La Manche. (6) Concerning F. Mildeanus 
Schimp. (7) New stations of F. Monguilloni Ther. (8) Remarks on 
No. 158 of the Musci Gallise. (9) F. crassipes Wils. var. Philiberti 
Besch. (10) F. Curnowii Mitt, in Tunis. A. G. 
Notes on Fissidens serrulatus Brid. and F. polyphyllus Wils.— 
G. Dismier {Revue Bryologique, 1920, 54-6). A discussion of the 
specific value of these two species which have sometimes been regarded 
as forms of one species. Authors have trusted too much to the 
character of the leaf — length and breadth, degree of denticulation at 
the apex, papillosity, presence or absence of a margin, position of 
inflorescence. But these are unstable ; and intermediate forms have 
been ascribed now to one, now to the other, of the two species, or have 
been proposed as independent species. However, the two species can 
be distinguished with ease and certainty in view of the anatomical 
characters pointed out by Bottini, in Malpighia , 1889, 3, 101-19, an 
interesting paper which is little known to bryologists. A resume of 
the specific differential characters is accordingly given by Dismier. 
They relate to the relative sizes of the cells in a transverse section of 
the stem, and also of certain cells in the leaf. The distribution of the 
two species is given. A. G. 
Observations on Didymodon cordatus Jur. — G. Dismier {Revue 
Bryologique, 1921, 52-3). This moss was regarded by Limpricht and 
by Warnstorf as an autonomous species, and by Dixon and by Amann 
as a sub-species of D. luridus ; but Dismier is convinced that it shows 
great affinity with the very polymorphic D. rigidulus, and is a sub- 
species of the latter, but not of D. luridus. A. G. 
